diff --git a/.github/workflows/rust.yml b/.github/workflows/rust.yml
index f95fc866..f1d339fa 100644
--- a/.github/workflows/rust.yml
+++ b/.github/workflows/rust.yml
@@ -43,8 +43,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: ['macos-latest', 'ubuntu-22.04', 'windows-latest']
-        rust: ['stable', '1.57']
+        os: ['macos-latest'] #, 'ubuntu-22.04', 'windows-latest']
+        rust: ['stable'] #, '1.57']
 
     runs-on: ${{ matrix.os }}
     steps:
@@ -83,7 +83,7 @@ jobs:
         run: echo "$env:VCPKG_DEFAULT_BINARY_CACHE/../vcpkg_installed/x64-windows/bin" | Out-File -FilePath $env:GITHUB_PATH -Append
         if: matrix.os == 'windows-latest'
 
-      - uses: Swatinem/rust-cache@v2
+      # - uses: Swatinem/rust-cache@v2
 
       - name: Build
         uses: actions-rs/cargo@v1
diff --git a/Cargo.lock b/Cargo.lock
index 3f08cb9d..5f406922 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -58,13 +58,22 @@ checksum = "233d376d6d185f2a3093e58f283f60f880315b6c60075b01f36b3b85154564ca"
 dependencies = [
  "addr2line",
  "cc",
- "cfg-if",
+ "cfg-if 1.0.0",
  "libc",
  "miniz_oxide",
  "object",
  "rustc-demangle",
 ]
 
+[[package]]
+name = "bincode"
+version = "1.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b1f45e9417d87227c7a56d22e471c6206462cba514c7590c09aff4cf6d1ddcad"
+dependencies = [
+ "serde",
+]
+
 [[package]]
 name = "bisection"
 version = "0.1.0"
@@ -166,6 +175,12 @@ dependencies = [
  "smallvec",
 ]
 
+[[package]]
+name = "cfg-if"
+version = "0.1.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4785bdd1c96b2a846b2bd7cc02e86b6b3dbf14e7e53446c4f54c92a361040822"
+
 [[package]]
 name = "cfg-if"
 version = "1.0.0"
@@ -194,6 +209,27 @@ version = "0.8.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "06ea2b9bc92be3c2baa9334a323ebca2d6f074ff852cd1d7b11064035cd3868f"
 
+[[package]]
+name = "crossbeam-channel"
+version = "0.4.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b153fe7cbef478c567df0f972e02e6d736db11affe43dfc9c56a9374d1adfb87"
+dependencies = [
+ "crossbeam-utils",
+ "maybe-uninit",
+]
+
+[[package]]
+name = "crossbeam-utils"
+version = "0.7.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c3c7c73a2d1e9fc0886a08b93e98eb643461230d5f1925e4036204d5f2e261a8"
+dependencies = [
+ "autocfg",
+ "cfg-if 0.1.10",
+ "lazy_static",
+]
+
 [[package]]
 name = "derive-into-owned"
 version = "0.2.0"
@@ -256,6 +292,28 @@ dependencies = [
  "rustc_version 0.3.3",
 ]
 
+[[package]]
+name = "fnv"
+version = "1.0.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3f9eec918d3f24069decb9af1554cad7c880e2da24a9afd88aca000531ab82c1"
+
+[[package]]
+name = "fuchsia-zircon"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2e9763c69ebaae630ba35f74888db465e49e259ba1bc0eda7d06f4a067615d82"
+dependencies = [
+ "bitflags 1.3.2",
+ "fuchsia-zircon-sys",
+]
+
+[[package]]
+name = "fuchsia-zircon-sys"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3dcaa9ae7725d12cdb85b3ad99a434db70b468c09ded17e012d86b5c1010f7a7"
+
 [[package]]
 name = "futures-channel"
 version = "0.3.21"
@@ -389,15 +447,26 @@ dependencies = [
  "system-deps",
 ]
 
+[[package]]
+name = "getrandom"
+version = "0.1.16"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8fc3cb4d91f53b50155bdcfd23f6a4c39ae1969c2ae85982b135750cccaf5fce"
+dependencies = [
+ "cfg-if 1.0.0",
+ "libc",
+ "wasi 0.9.0+wasi-snapshot-preview1",
+]
+
 [[package]]
 name = "getrandom"
 version = "0.2.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c05aeb6a22b8f62540c194aac980f2115af067bfe15a0734d7277a768d396b31"
 dependencies = [
- "cfg-if",
+ "cfg-if 1.0.0",
  "libc",
- "wasi",
+ "wasi 0.11.0+wasi-snapshot-preview1",
 ]
 
 [[package]]
@@ -642,6 +711,34 @@ dependencies = [
  "mach2",
 ]
 
+[[package]]
+name = "iovec"
+version = "0.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b2b3ea6ff95e175473f8ffe6a7eb7c00d054240321b84c57051175fe3c1e075e"
+dependencies = [
+ "libc",
+]
+
+[[package]]
+name = "ipc-channel"
+version = "0.15.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ad9b32d360ae2d4662212f1d29bc8a277256f49029cea20fd6c182b89819aea7"
+dependencies = [
+ "bincode",
+ "crossbeam-channel",
+ "fnv",
+ "lazy_static",
+ "libc",
+ "mio",
+ "rand 0.7.3",
+ "serde",
+ "tempfile",
+ "uuid",
+ "winapi 0.3.9",
+]
+
 [[package]]
 name = "itertools"
 version = "0.12.1"
@@ -657,6 +754,22 @@ version = "1.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4217ad341ebadf8d8e724e264f13e593e0648f5b3e94b3896a5df283be015ecc"
 
+[[package]]
+name = "kernel32-sys"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7507624b29483431c0ba2d82aece8ca6cdba9382bff4ddd0f7490560c056098d"
+dependencies = [
+ "winapi 0.2.8",
+ "winapi-build",
+]
+
+[[package]]
+name = "lazy_static"
+version = "1.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
+
 [[package]]
 name = "libc"
 version = "0.2.153"
@@ -696,6 +809,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "maybe-uninit"
+version = "2.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "60302e4db3a61da70c0cb7991976248362f30319e88850c487b9b95bbf059e00"
+
 [[package]]
 name = "memchr"
 version = "2.7.1"
@@ -729,6 +848,59 @@ dependencies = [
  "adler",
 ]
 
+[[package]]
+name = "mio"
+version = "0.6.23"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4afd66f5b91bf2a3bc13fad0e21caedac168ca4c707504e75585648ae80e4cc4"
+dependencies = [
+ "cfg-if 0.1.10",
+ "fuchsia-zircon",
+ "fuchsia-zircon-sys",
+ "iovec",
+ "kernel32-sys",
+ "libc",
+ "log",
+ "miow",
+ "net2",
+ "slab",
+ "winapi 0.2.8",
+]
+
+[[package]]
+name = "miow"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ebd808424166322d4a38da87083bfddd3ac4c131334ed55856112eb06d46944d"
+dependencies = [
+ "kernel32-sys",
+ "net2",
+ "winapi 0.2.8",
+ "ws2_32-sys",
+]
+
+[[package]]
+name = "mitosis"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7012dfe1df20be7df25c8ec0d855fb1a72054e10c75481d4702c1719c829d5be"
+dependencies = [
+ "ipc-channel",
+ "lazy_static",
+ "serde",
+]
+
+[[package]]
+name = "net2"
+version = "0.2.39"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b13b648036a2339d06de780866fbdfda0dde886de7b3af2ddeba8b14f4ee34ac"
+dependencies = [
+ "cfg-if 0.1.10",
+ "libc",
+ "winapi 0.3.9",
+]
+
 [[package]]
 name = "num-format"
 version = "0.4.4"
@@ -812,13 +984,14 @@ dependencies = [
  "itertools",
  "lrumap",
  "memmap2",
+ "mitosis",
  "num-format",
  "num_enum",
  "nusb",
  "once_cell",
  "page_size",
  "pcap-file",
- "rand",
+ "rand 0.8.5",
  "rand_xorshift",
  "serde",
  "serde_json",
@@ -832,7 +1005,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "30d5b2194ed13191c1999ae0704b7839fb18384fa22e49b57eeaa97d79ce40da"
 dependencies = [
  "libc",
- "winapi",
+ "winapi 0.3.9",
 ]
 
 [[package]]
@@ -960,6 +1133,19 @@ dependencies = [
  "proc-macro2",
 ]
 
+[[package]]
+name = "rand"
+version = "0.7.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6a6b1679d49b24bbfe0c803429aa1874472f50d9b363131f0e89fc356b544d03"
+dependencies = [
+ "getrandom 0.1.16",
+ "libc",
+ "rand_chacha 0.2.2",
+ "rand_core 0.5.1",
+ "rand_hc",
+]
+
 [[package]]
 name = "rand"
 version = "0.8.5"
@@ -967,8 +1153,18 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "34af8d1a0e25924bc5b7c43c079c942339d8f0a8b57c39049bef581b46327404"
 dependencies = [
  "libc",
- "rand_chacha",
- "rand_core",
+ "rand_chacha 0.3.1",
+ "rand_core 0.6.4",
+]
+
+[[package]]
+name = "rand_chacha"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f4c8ed856279c9737206bf725bf36935d8666ead7aa69b52be55af369d193402"
+dependencies = [
+ "ppv-lite86",
+ "rand_core 0.5.1",
 ]
 
 [[package]]
@@ -978,7 +1174,16 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e6c10a63a0fa32252be49d21e7709d4d4baf8d231c2dbce1eaa8141b9b127d88"
 dependencies = [
  "ppv-lite86",
- "rand_core",
+ "rand_core 0.6.4",
+]
+
+[[package]]
+name = "rand_core"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "90bde5296fc891b0cef12a6d03ddccc162ce7b2aff54160af9338f8d40df6d19"
+dependencies = [
+ "getrandom 0.1.16",
 ]
 
 [[package]]
@@ -987,7 +1192,16 @@ version = "0.6.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ec0be4795e2f6a28069bec0b5ff3e2ac9bafc99e6a9a7dc3547996c5c816922c"
 dependencies = [
- "getrandom",
+ "getrandom 0.2.8",
+]
+
+[[package]]
+name = "rand_hc"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ca3129af7b92a17112d59ad498c6f81eaf463253766b90396d39ea7a39d6613c"
+dependencies = [
+ "rand_core 0.5.1",
 ]
 
 [[package]]
@@ -996,7 +1210,7 @@ version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d25bf25ec5ae4a3f1b92f929810509a2f53d7dca2f50b794ff57e3face536c8f"
 dependencies = [
- "rand_core",
+ "rand_core 0.6.4",
 ]
 
 [[package]]
@@ -1162,7 +1376,7 @@ version = "3.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "01ce4141aa927a6d1bd34a041795abd0db1cccba5d5f24b009f694bdf3a1f3fa"
 dependencies = [
- "cfg-if",
+ "cfg-if 1.0.0",
  "fastrand",
  "redox_syscall",
  "rustix",
@@ -1233,6 +1447,15 @@ version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8ccb82d61f80a663efe1f787a51b16b5a51e3314d6ac365b08639f52387b33f3"
 
+[[package]]
+name = "uuid"
+version = "0.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bc5cf98d8186244414c848017f0e2676b3fcb46807f6668a97dfe67359a3c4b7"
+dependencies = [
+ "getrandom 0.2.8",
+]
+
 [[package]]
 name = "version-compare"
 version = "0.1.0"
@@ -1245,12 +1468,24 @@ version = "0.9.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "49874b5167b65d7193b8aba1567f5c7d93d001cafc34600cee003eda787e483f"
 
+[[package]]
+name = "wasi"
+version = "0.9.0+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cccddf32554fecc6acb585f82a32a72e28b48f8c4c1883ddfeeeaa96f7d8e519"
+
 [[package]]
 name = "wasi"
 version = "0.11.0+wasi-snapshot-preview1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9c8d87e72b64a3b4db28d11ce29237c246188f4f51057d65a7eab63b7987e423"
 
+[[package]]
+name = "winapi"
+version = "0.2.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "167dc9d6949a9b857f3451275e911c3f44255842c1f7a76f33c55103a909087a"
+
 [[package]]
 name = "winapi"
 version = "0.3.9"
@@ -1261,6 +1496,12 @@ dependencies = [
  "winapi-x86_64-pc-windows-gnu",
 ]
 
+[[package]]
+name = "winapi-build"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2d315eee3b34aca4797b2da6b13ed88266e6d612562a0c46390af8299fc699bc"
+
 [[package]]
 name = "winapi-i686-pc-windows-gnu"
 version = "0.4.0"
@@ -1413,3 +1654,13 @@ checksum = "a7cad8365489051ae9f054164e459304af2e7e9bb407c958076c8bf4aef52da5"
 dependencies = [
  "memchr",
 ]
+
+[[package]]
+name = "ws2_32-sys"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d59cefebd0c892fa2dd6de581e937301d8552cb44489cdff035c6187cb63fa5e"
+dependencies = [
+ "winapi 0.2.8",
+ "winapi-build",
+]
diff --git a/Cargo.toml b/Cargo.toml
index 6712d3b0..138d09f6 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -38,6 +38,7 @@ serde = { version = "1.0.196", features = ["derive"] }
 serde_json = "1.0.113"
 rand = "0.8.5"
 rand_xorshift = "0.3.0"
+mitosis = "0.1.1"
 
 [features]
 step-decoder = []
@@ -46,12 +47,6 @@ test-ui-replay = ["serde", "serde_json"]
 debug-region-map = []
 test-cynthion = []
 
-[[test]]
-name = "test_replay"
-path = "src/test_replay.rs"
-harness = false
-required-features = ["test-ui-replay"]
-
 [[test]]
 name = "test_cynthion"
 path = "src/test_cynthion.rs"
diff --git a/src/main.rs b/src/main.rs
index abe98bcd..b318e2f1 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -16,3 +16,6 @@ fn main() {
     application.run_with_args::<&str>(&[]);
     display_error(stop_cynthion());
 }
+
+#[cfg(test)]
+mod test_replay;
diff --git a/src/test_replay.rs b/src/test_replay.rs
index 1a981cf6..e1f9ba32 100644
--- a/src/test_replay.rs
+++ b/src/test_replay.rs
@@ -20,7 +20,29 @@ use packetry::ui::{
     with_ui,
 };
 
-fn main() {
+// On systems other than macOS we can run this as a normal unit test.
+#[cfg(not(target_os="macos"))]
+#[test]
+fn test_replay() {
+    run_test();
+}
+
+// On macOS, GTK must run on the main thread, so we spawn a new process.
+#[cfg(target_os="macos")]
+#[test]
+fn mitosis() {
+    mitosis::init_test();
+}
+
+#[cfg(target_os="macos")]
+#[test]
+fn test_replay() {
+    mitosis::init_test();
+    let process = mitosis::spawn((), |_| run_test());
+    process.join().unwrap();
+}
+
+fn run_test() {
     let application = gtk::Application::new(
         Some("com.greatscottgadgets.packetry.test"),
         Default::default(),